For the past couple of months, we've asked, hoped and dreamed for it, and today, AMD is launching it - the $354 Athlon 64 X2 3800+; the first somewhat affordable dual core CPU from AMD.

If necessity is the mother of invention, then the birth of the Athlon 64 X2 3800+ should be no surprise to anyone. In one of their strongest CPU paper-launches ever, AMD put their best foot forward this past May and introduced the Athlon 64 X2 processor. While AMD was late to the desktop dual core game compared to Intel, the Athlon 64 X2 processor had absolutely no problem outperforming Intel's Pentium D. But at the end of the day, despite AMD's clear victory, our recommendations were quite complicated, thanks to one major flaw in AMD's execution: price.

The cheapest dual core Pentium D processor could be had for under $300, yet AMD's cheapest started at $537. Intel was effectively moving the market to dual core, while AMD was only catering to the wealthiest budgets.

The Pentium D 820, running at 2.8GHz and priced at $280, offered the most impressive value that we've seen in a processor in quite some time - if you could properly use the power. Multitaskers and users of multithreaded applications found themselves with the cheapest 2-way workstation processor that they had seen since the SMP Celerons and ABIT's BP6. While Intel satiated our demands for affordable dual core, we knew it wasn't the perfect option. AMD's Athlon 64 X2 was the better overall performer, just at the very wrong price point.

After much pressure from all sides and some very important manufacturing changes, AMD went ahead with the decision to release a cheaper Athlon 64 X2. The decision was made around the time of Computex 2005 and that's when we first heard of the $354 Athlon 64 X2 3800+.

The Athlon 64 X2 3800+ is basically two Athlon 64 3200+ cores stuck together, each running at 2.0GHz and each with its own 512KB L2 cache. This is a full 200MHz lower clock per core than the 4200+, but with the same amount of cache.

Note: The 512KB X2s are available in both 154M and 233M transistor versions.

Looking at the table above, it is clear that AMD has left room for another SKU - potentially an Athlon 64 X2 4000+ at 2.0GHz, but with a 1MB L2 cache. AMD could also go lower, pairing up a couple of 1.8GHz/512KB cores, but AMD most likely wanted to find a good balance between single threaded performance, price and multithreaded performance with this new "entry level" X2 core.

A New Core

AMD didn't sit on the X2 3800+ just because they were greedy and expected everyone to gobble up the $500+ parts. Instead, today's release is the result of a slightly revised core, codenamed Manchester, specifically designed to cut costs.

The original Athlon 64 X2 (Toledo core) processors all had the same exact specifications:

- 233.2M transistors
- 199 mm2 die size
- 110W max power

For the Athlon 64 X2 4800+ and the 4400+, the shared transistor count and die size made sense. They both were identical from a transistor standpoint, one chip just ran 200MHz faster than the other. But the 4200+ and the 4600+ weren't identical; unlike the 4800/4400+ X2s, the 4200+ and 4600+ only had a 512KB L2 cache per core, not a 1MB L2.

Update: As many of you have correctly pointed out, the 4200+ and 4600+ were available as both Toledo and Manchester cores. More than half of the Athlon 64 X2's transistor count is spent on cache, which means that if there are going to be any manufacturing defects on the chip, they will more than likely occur in the processor's cache. Born out of that fact, the Toledo based Athlon 64 X2 4600+ and 4200+ were nothing more than 4800/4400+ X2s with too many manufacturing defects; instead of throwing the bad cores away, AMD simply rebranded them and sold them at lower price points. The problem with this approach is that an Athlon 64 X2 4200+ took the same amount of space on a wafer as an Athlon 64 X2 4800+, despite only having half the cache. Thus we have the Manchester core: a core designed from the ground up to only feature a 512KB L2 cache per core.

As manufacturing ramps up, yields improve and it is now possible to actually create a cost-reduced Athlon 64 X2, using the smaller Manchester die - and that's where the Athlon 64 X2 3800+ gets its cost savings.

The transistor count of the 3800+ goes down to 154 million, and the die gets shrunk down to 147 mm2 compared to the 233.2M and 199 mm^2 of its bigger brothers (4800/4400+). The thermal envelope of the new core also dropped from 110W down to 89W, both still lower than Intel's Pentium D or single-core Pentium 4 for that matter.

With a smaller die and lower transistor count, the Athlon 64 X2 3800+ is able to support its $354 price tag.

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109 Comments

ISTM that the choice of Intel mobo is mistated. Further, IMO using an ASUS high-end mobo as one test platform and any Intel mobo as the other gives the former at least a 3% - 5% performance advantage. I wonder too, were all of the ASUS mobo's oc features turned off?

"The Test
Our hardware configurations are similar to what we've used in previous comparisons. For this test, we focused on CPUs at or around the Athlon 64 X2 3800+'s $354 price point.

Rendering in 3dstudio max benefits from dualcore cpus. It however, also benefits from hyperthreading if this is a mental ray render. I'd like to see results for the pentium-d and amd-x2 when rendering in 3dstudio 7 with mental ray. I think the advantage is significant, especially in video renders as it's mathematically more effective to have more nodes rendering.

very nice article indeed! know i just received three computers from Dell today with Pentium D processors, so i see the new X2 is a bit faster, but excited to try it out in general multi-tasking environments regardless.

One question i haven't seen answered is: How does a dual-core cpu compare against a true SMP dual-cpu system? Example would be a Pentium D 840 (or AMD X2 4200+) vs. 2x Pentium 4 - 2.8 GHz Xeon system? For the price, dual-core seems great. How does it handle running Windows 2000 Server or 2003 Server or running as an Exchange server?

If anyone has any input or has tried this, I'd be interested in knowing.

Oh... also, since AMDs cache coherency implementation and the way the dual cores work is more efficient than Intel's, so applications that have to pass ownership of cached data (L1/L2) back and forth a lot will be faster on AMD X2 machines. Of course, this type of application behavior is usually considered to be the result of poor design, so use well written apps :) Reply

Actually, I'd give a slight (very slight) edge to Intel's approach on SMP systems....though AMD's Hypertransport is certainly far cleaner on paper, it hasn't paid off quite so well in practice. However, HT is considerably more suited for a NUMA-based multi-cpu architecture than for SMP. Unfortunately, there aren't many NUMA OS's out there at the moment... Reply

One question i haven't seen answered is: How does a dual-core cpu compare against a true SMP dual-cpu system?

Depends. Dual CPU systems and dual core systems both have two cores running in them. The main difference is that two single core AMD machines (two Opterons) can have independent memory banks if you buy an appropriate motherboard. The dual core systems 9(both Intel's and AMD's) share the same pipe to memory. This isn't as big of an issue for AMD parts because the Athlon64 (single core) really doesn't make good use of dual channel memory anyway (dual channel over single channel is at best 20% faster in memory intensive apps while most see around 5%) so neither of the cores in the dual core setup get memory starved unless both cores are running full tilt (by benchmarks, I guess this would mean that if single channel were 1, dual channel were 2, the two cores running full tilt would need 2.4 channel memory to never be starved). The Intel parts, however, will suffer more. Dual channel memory on a P4 can be saturated by a single core so dual cores going all out can become starved a bit worse (one core would be 2, two cores would need 4/quad channel memory to never be starved).

So, your performance will depend on what types of applications you will be running. Reply

Well Im missing the reasons for comparing the 640 Intel,and 630 D Intel when both are less than the AMD 3800+,and 3800+x2.

True if you where to take the 'best of'in performance to price between both Intel,and Amd the 640 Pentium 3.2 would be the comparitor .

Performance alone though,true AMD 3800+ surpasses the P4 640 .The 3500+ AMD 64 would have been a closer comparitive if solely on a price basis.

With both the AMD 3500+,or the Intel 640 to be either choice in that price point to have. They compare in performance as well.Especially since the next Pentium pricepoint the 3.4 Ghz 650 is the closer comparitor.

The 3800+ AMD 939 single is still more expensive than the Dual-Core 830 D . With the newest AMD 3800+ still at the 400$ spot.

Comparing the Intel 640 to the 3800+AMD is lopsided.

The Intel 650 is the closer comparator,in terms of cost.Still though the Intel 640 remains the gulf between them when cost is the comparator.

Im missing reason author chose to compare these specific CPUs. Since the Intel is clearly not in same performance class.Although for even reach of benchmarks,would be the best'of''in price points to beat.Should have compared the Intel 650,to the AMD 3800+.

AMD 64 3500,AMD 64 3700 would have been closer comparitors to cost between the two,to match up performance.Seen the benchmarks before between them.AMD winning some,Intel winning some.Howebeit,the Intel has HT.etc.

Once again, I believe Anand has shown un-biased data. I run a Dell hyperthreading rig, just because its convenient. BUT, as others have pointed, the X2's were designed from the ground up to be dual, on chip. To have to leave the core, and use the FSB, just shows that Intel is playing catch up. Benchmarks can, and often do show whatever the person running the benchmark wishes to show. Anand has ALWAYS, IMHO, tried to show, unbiased, accurate DATA. The basic design of the long piped Pentium will almost always favor Intel in benchmarks which, in essence are SIMD, in nature. That is, processing streams of data, with a single instuction. Price points, for ANY given CPU, GPU, HDD etc will always be Market Driven. The complexities, which go into the pricing decisions are well beyond the scope of this forum IMHO. AMD will continue to offer innovative design, over Intels 'brute force', more megahertz must be better, approach. Reply